Pulsed neutron generated prompt gamma emission measurement system for surface defect detection and analysis

Abstract

A method of determining structural defects in a component that utilizes neutron activation of a solution having the ability to penetrate small cracks on the surface of a material via capillary absorption that produces a discernable prompt gamma release of a defined energy when exposed to a neutron pulse. The intensity of the gamma rays produced at the desired energy at a user controlled position on the surface is used to determine the crack location, length and depth.

Description

BACKGROUND[0001]1. Field[0002]This invention relates in general to the detection of cracks in irradiated surfaces and, more particularly, the nondestructive examination of irradiated components to determine structural flaws.[0003]2. Related Art[0004]In the event highly radioactive components or the containers of radioactive materials need to be manipulated, it is important to ensure the structural integrity of the components or material containers be assessed to minimize the potential for loss of control and containment of the radioactive material. The structural integrity of radioactive components or containers of radioactive materials resident in high radiation fields is difficult to assess using standard visual and ultrasonic Non-Destructive Examination (NDE) techniques due to the impact the radiation field has on equipment access and operability. A need exists to provide a means to evaluate the structural integrity of radioactive components and containers of radioactive material...

AI Technical Summary

Benefits of technology

[0005]This invention discloses a method of nondestructively detecting structural defects in a surface of an irradiated material comprising the step of applying a liquid crack penetrant, preferably one high in Nitrogen content, or one that is mixed with a chemical species containing a large proportion of an isotope that has a relatively large fast neutron prompt capture gamma emission cross section, such as Scandium, Vanadium, Manganese or Titanium, that emits a prompt gamma release of a defined energy, to a surface of the material. The surface is then irradiated with a neutron pulse generator and a plurality of beta radiation detectors tuned to the defined energy, are positioned in a regular pattern over the surface of the material to which the mixture is applied to; the plurality of beta radiation detectors respectively providing an output indicative of a reception of the prompt gamma release of the defined energy in an area of the surface viewed by a corresponding one of the beta radiation detectors. The reception is employed to map a characteristic of the defect. In one embodiment the characteristic is the location and length of the defect on the surface. In another embodiment, the characteristic is the depth of the defect on the surface. Preferably, the depth of the defect is determined from the strength of the reception.

[0006]In one such embodiment, the mixture is absorbed into the surface by capillary absorption. Desirably, the neutron pulse generator is a neutristor style Neutron Pulse Generator. Preferably, the tuning of the beta radiation detectors is accomplished by placing a high atomic number sacrificial material between the surface and an active portion of the beta radiation detectors to act as an electron radiator. Desirably, the beta radiation detectors are silicon carbide (SiC) detectors with the thickness, distance from the active detector region, and type of material used in the sacrificial layer of the beta radiation detector elected to ensure that mostly the electrons produced by Photoelectric Absorption by the desired emitted prompt gamma radiation energy are completely stopped inside the active region of the SiC detectors. In one such embodiment the sacrificial material is either platinum or tungsten.

Problems solved by technology

The structural integrity of radioactive components or containers of radioactive materials resident in high radiation fields is difficult to assess using standard visual and ultrasonic Non-Destructive Examination (NDE) techniques due to the impact the radiation field has on equipment access and operability.

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